High-z AGN Candidates in COSMOS Anton Koekemoer (STScI) + F. Civano, M. Elvis, V. Mainieri, J. Trump, E. Treister, T. Murayama, T. Nagao, Y. Oyama, Y. Taniguchi, M. Brusa, C. Carilli, P.Capak, A. Comastri, E. Daddi, F. Fiore, G. Hasinger, O. Ilbert, C. Impey, K. Jahnke, A. Martínez-Sansigre, H. McCracken, A. Merloni, B. Mobasher, M. Salvato, D. Sanders, S. Sasaki, E. Schinnerer, N. Scoville, J. Silverman, V. Smolcic, G. Zamorani, +…

Black holes in context: Likely tracer of hierarchical dark matter halos Provide hard ionizing continuum, relevant to low-  reionization May regulate galaxy growth / SFR via feedback M-  relation suggests intimate connection between BH/galaxy formation and growth To date: At z ~ , already have supermassive BHs to ~ 10 9 M o ( Fan et al ; Willott et al. 2003; Vestergaard et al ) AGN LF evolves strongly from z~6 to z~2; PLE is ruled out ( Fan et al ; Richards et al ) Faint end of AGN LF steepens at z~6 ( Jiang et al 2009, Fan et al. (Richards et al. 2006)

Questions: How do the most massive BHs form within < 1 Gyr? How does BH growth influence the M-  relation? What is the ionizing budget of AGN integrated over the LF beyond z ~ 6, and its contribution to reionization? (How) does obscured/unobsc. AGN ratio evolve at high z? Our knowledge has been limited by the following: only the top of the AGN LF has been studied at z ~ 6 no AGN previously confirmed at z > 7 Approach: Understand AGN / SFR evolution at z ~ Set out to quantify the faint end of AGN LF at z ~ 6 Search for more luminous AGN at z > ~ 6 - 7

Selection Criteria: X-ray properties: Well-detected in X-rays (~ erg s -1 cm -2 ) F X /F Opt is a lower limit, and is > ~100x above the average for AGN Generally have soft and hard X-ray emission (excludes z<2 obscured AGN) z-K colour: most AGN with F X /F Opt ~ have fairly tight z-K ~1-2, with some slight scatter: –z-K ~ -1 to 2 for quasars/Seyferts –z-K ~ 2 to 4 for ERO’s high-z candidates have z-K >4

Optical dropout X-ray sources ACS- i K SPITZER/IRAC1,2,3,4

SED fitting: Explore a full grid of parameters to differentiate high-z from lower-z (eg z~2-3 “red and dead” DRGs, etc): –Charlot & Bruzual (2003), also Maraston ( ) –combine SSP + CSP –reddening laws (Calzetti, LMC, SMC, galactic) Several sources can have 2 redshift peaks (z~2-3 plus a high-z alternative), exclude these as low-z interlopers

Best 2 candidates to date: Undetected in ACS and Subaru i,z bands to AB~27 Detected in J, K at AB~23 Relatively “blue” SEDs from K through IRAC These were the only 2 left after excluding other sources with intermediate/low-z SED solutions

MOIRCS Spectroscopy - progress to date… SED fitting is useful but really need to get IR spectra Subaru - MOIRCS: ~4 hours/mask; objects faint (K~23+) Data reduction currently in progress (thanks to Youchi Oyama for help!)

Late-breaking news: Cyc 18 WFC3/IR grism spectrocopy time awarded! Observational design: –Total of 8 orbits per source –4 orbits in G102, 4 orbits in G141 –Full spectral coverage from micron –Multiple visits (at orients deg apart) Science Goals: robust detection of continuum, along with emission lines, to provide: –emission line detection for redshift determination –Underlying stellar continuum for SFR determination –If CIV is detected, estimate virial BH mass Stay tuned!…